The present invention relates to a carbon heating element having excellent durability even when repeatedly used in a high-temperature environment, and a method of manufacturing the same.
Nichrome and carbon materials are generally used as heating elements.
Nichrome wires are not usable in an atmosphere of a halogen gas, an acid gas, a corrosive gas or the like. In such a special environment, carbon materials are utilized because of their chemical stability. Carbon materials, however, are not usable in an environment in which a strong oxidizing chemical, such as concentrated nitric acid or fuming concentrated nitric acid, is generated.
Further, carbon materials can be used in a high-temperature environment only if the atmosphere is non-oxidizing, and are not usable in air at a temperature higher than about 400xc2x0 C., since air oxidizes carbon materials.
Known carbon heating elements usable in air at a high temperature of 400xc2x0 C. or more include carbon heating elements comprising a ceramic or glass covering material on the surface of a carbon material to thereby protect the carbon material from oxygen. In such carbon heating elements, the covering material is in complete contact with the surface of the carbon material, so as to block oxygen and protect the inside carbon material from oxidation.
However, the covering material and the carbon material are different from each other in expansion coefficient, so that the covering material will peel off and lose its covering effect when repeatedly used. Further, these heating elements are limited in application because the covering material has low thermal shock resistance.
The present invention solves or remarkably reduces the problems of the prior art. The main object of the present invention is to provide a carbon heating element having excellent durability to withstand repeated use even when heated in air at about 1000xc2x0 C.
Another object of the present invention is to provide a carbon heating element having excellent thermal shock resistance to withstand rapid temperature change.
A further object of the present invention is to provide a carbon heating element usable in a special environment such as in a strong oxidizing chemical.
A still further object of the present invention is to provide a carbon heating element having a capacity to generate sufficient heat with lower power consumption.